The invention relates to a header tube for a heat exchanger, with one or more slots for the insertion of a respective flat tube, said slots being introduced by punching with no inner die or by internal high-pressure forming, and to a method for the production of a header tube of this type. An important field of use is heat exchangers in the form of evaporators and condensers or gas coolers of motor vehicle air-conditioning systems.
Patent Specifications EP 0 198 581 B1 and U.S. Pat. No. 5,052,480 disclose header tubes, each with a row of transverse slots, into which are inserted flat-tube ends of a heat exchanger block constructed from flat tubes arranged in parallel. Due to the transverse position of the slots, the header tube diameter must be kept larger than the slot length. The header tubes have a tube-wall thickness which is smaller by a multiple than their diameter. Due, inter alia, to this small tube-wall thickness, as regards the header tubes of EP 0 198 581 B1, indentations of the header tube occur in the regions of the slots and form inwardly bent intrusions, the tube outside diameter being about one and a half times larger outside the slot region than in the slot region.
In a header tube production method described in the laid-open publication DE 43 34 203 A1, transverse slots in the form of inwardly bent intrusions are introduced into a header tube by punching assisted by an inner die, for which purpose an inner die is pushed into the header tube and the slots are punched into the header tube wall from outside by means of a suitable ram.
Alternatively to transverse slots, it is known to provide header tubes with slots which run parallel to or at an acute angle to the tube longitudinal axis and into which twisted flat-tube ends are inserted, see for example, Patent Specification U.S. Pat. No. 3,416,600 and the laid-open publications EP 0 845 648 A2 and DE 197 29 497 A1.
The technical problem on which the invention is based is to provide a header tube of the type mentioned in the introduction, which can be produced at relatively low outlay and is also suitable, in particular, for applications involving a high pressure load, such as for CO2 air conditioning systems of motor vehicles, and an advantageous method for the production of such a header tube.